Ukraine’s chief prosecutor has seemingly frozen four investigations into Paul Manafort, President Donald Trump’s former campaign chairman, in an effort to avoid “irritating” American officials.

This occurred as the Ukrainian government sought to purchase anti-tank missiles known as Javelins from the US.

Manafort is currently facing prosecution in the US over charges of money laundering and financial fraud linked to his work for a pro-Russian political party in Ukraine.

Ukraine’s chief prosecutor has seemingly frozen four investigations into Paul Manafort, President Donald Trump’s former campaign chairman, in an effort to avoid “irritating” American officials.

The investigations have not been closed altogether, but the decision to halt them effectively blocked the prosecutor from issuing subpoenas for evidence or interviewing witnesses. This occurred as the Ukrainian government sought to purchase anti-tank missiles known as Javelins from the US,The New York Times reports.

Manafort is currently facing prosecution in the US over charges of money laundering and financial fraud linked to his work for a pro-Russian political party in Ukraine.

Ukrainian officials are apparently aware of Trump’s dismay over the ongoing investigation into his campaign’s alleged collusion with Russian election interference, lawmakers told The Times, which seems to have motivated the decision to halt investigations into Manafort’s activities.

On Wednesday, Trump once again took to Twitter to vent about the investigation, tweeting, “There was no Collusion (it is a Hoax) and there is no Obstruction of Justice (that is a setup & trap). What there is is Negotiations going on with North Korea over Nuclear War, Negotiations going on with China over Trade Deficits, Negotiations on NAFTA, and much more. Witch Hunt!”

Meanwhile, the US government has been one of Ukraine’s staunchest allies in the fight against pro-Russian forces in eastern Ukraine. The Ukrainian government apparently doesn’t want to do anything to jeopardize this.

Volodymyr Ariev, a member of Ukraine’s parliament, told The Times the the investigation’s into Manafort have more or less been placed “in the long-term box.”

“In every possible way, we will avoid irritating the top American officials. We shouldn’t spoil relations with the administration,” Ariev said.

Another lawmaker, Andrey Derkach, claimed pursuing an investigation into Manafort put US aid to Ukraine at risk. “Everybody is afraid of this case” in Ukraine, he told The Times.

Until the investigations were halted, Ukrainian officials were looking into money paid to Manafort and a New York-based law firm by people within former Ukrainian President Viktor Yanukovych’s political party. Yanukovych, who was pro-Russian, was famously ousted in 2014 by street protests that captured the world’s attention and ultimately spiraled into the conflict that continues to rage on in eastern Ukraine. Manafort was a long-time adviser of Yanukovych.

The Ukrainian government’s decision to halt the investigations into Manafort reportedly came in April, roughly a month after the Pentagon gave the final approval for the sale of 210 Javelins and 35 launching units to Ukraine. Ukraine received the missiles on April 30.

Ukraine has long sought these missiles in order to shift the balance in the fight against pro-Russian forces in eastern Ukraine. Over 10,000 people have been killed as a result of the fighting in this region, which began after Russia’s annexation of Crimea in March 2014.